The present invention relates to a method for mixing steel fiber in concrete or mortar.
Recently, methods of improving the tensile strength, crack resistance, toughness, etc. of concrete or mortar by mixing steel fiber with the diameter of about 0.2-0.5 m/m and length of about 30-50 m/m in the concrete or mortar for public works and construction have been studied in various countries with much success. On the other hand, a method of manufacturing the abovementioned steel fiber with efficiency and in large quantities is being developed. Accordingly, it is apparent that concrete or mortar which is reinforced by steel fiber will be industrially used on an extensive scale in the near future. There, however, is a problem at present as to the method of mixing the abovementioned steel fiber in concrete or mortar. Namely, it is necessary that the aforesaid steel fiber is spread evenly in concrete or mortar, the direction of the fiber being arranged at random, while the abovementioned steel fiber is evenly spread in concrete or mortar in order that the concrete or mortar mixed with steel fiber may fully perform its function. And it is necessary to mix steel fiber in considerably great quantities in concrete or mortar in a short period of time in order that it is utilized industrially (e.g., it is said to be necessary to mix around 100 kg of steel fiber for concrete of 1m.sup.3 and that it is necessary to dispose about 100 kg. of steel fiber in about three minutes in the case of compounding the abovementioned concrete at one step). Conventionally, however, only inefficient methods such as spreading fiber on concrete or mortar after disentangling it by hand or spreading steel fiber on concrete or mortar after sieving the short fiber which was disentangled by a rake or a rotating claw have been devised and an efficient method thereof is being groped in each country of the world under the present state.